NATURAL AND HUMAN INDUCED HAZARDS – Vol. I - Geography of Volcanic Zones and Distribution of Active Volcanoes - V. Yu. Kirianov GEOGRAPHY OF VOLCANIC ZONES AND DISTRIBUTION OF ACTIVE VOLCANOES V. Yu. Kirianov Institute of Volcanic Geology and Geochemistry RAS, Petropavlovsk-Kamchatsky, Russia Keywords: volcanoes, Pacific, island arc, eruption, crust Contents 1. Introduction 2. Volcanoes of the Pacific Ocean Island Arcs and Alaska Continental Rim 2.1. Frontal Island Arcs of the Pacific Ocean 2.2. Inner Island Arcs of the Pacific Ocean 2.3. Reverse Island Arcs of Pacific Ocean 3. Volcanoes of the East Pacific Continental Rim 3.1. Cascade Volcanoes 3.2. Mexican Volcanic Belt 3.3. Guatemala–Nicaragua zone 3.4. Columbia–Ecuador zone 3.5. Peru–Bolivian Zone 3.6. Argentina–Chilean zone 4. Volcanoes of Alpine-Indonesian Mountain belt 4.1. Alpine-Himalayan System 4.2. Burma–Indonesian System 5. Volcanoes of East African–Arabian Belt 5.1. Arabian–Nubian High 5.2. East Africa High 6. Volcanoes of Rifts and Mountains of Eurasia 6.1. Manchuria 6.2. Far Northeast Asia 7. Volcanoes of the West Indies Island Arc 8. Volcanoes of the Ocean Floor 8.1. Iceland UNESCO – EOLSS 8.2. Mid-Atlantic Islands 8.3. Hawaii 8.4. Indian Ocean 8.5. Submarine SAMPLEVolcanoes CHAPTERS 9. Conclusions Acknowledgments Glossary Bibliography Biographical Sketch Summary Volcanic eruptions are the most awesome and powerful display of nature’s force. Every ©Encyclopedia of Life Support Systems (EOLSS) NATURAL AND HUMAN INDUCED HAZARDS – Vol. I - Geography of Volcanic Zones and Distribution of Active Volcanoes - V. Yu. Kirianov year about 50 volcanoes throughout the world are active above sea level. There are more than 500 active volcanoes (those that have erupted at least once within recorded history) in the world. A map of the world’s active volcanoes shows them to be distributed unequally on Earth’s surface, concentrated in some areas and completely lacking in others. Some volcanoes crown island areas near the continents, others form chains of islands in the deep ocean basins. About 62% of all active volcanoes in the world are located around the margins of the Pacific Ocean, although their distribution along this rim is irregular. Continental margin volcanism is connected with geologically young mountain fold belts. Belts of intracontinental volcanism extending from southeastern Europe through the Mediterranean, southern Asia, and into the East Indies archipelago, and the African– Arabian mountain belt crossing the African continent. The Hawaiian Islands provide the best example of an “intraplate” volcanic chain, developed by the northwest-moving Pacific plate passing over an inferred “hot spot” that initiates the volcano-formation process. More or less isolated volcanoes occur within each of the three great oceanic regions of the world, the Pacific, the Atlantic, and the Indian Ocean and the eastern continental margin of Eurasia. 1. Introduction Volcanism is an extremely powerful process of melting, differentiation, and segregation in the hot interior of planets that has been ongoing on Earth since the initial stages of its evolution over 4 billion years ago. Volcano eruptions on land in the last century alone have produced one and half billion tons of material per year, while the volume of basalts erupted by submarine volcanoes in mid-ocean rifts and along fracture zones is several times higher. Earth’s hydrosphere and atmosphere are composed to a large extent of water vapor, carbon dioxide, and other volatiles that originated from volcanic emanations throughout the long history of the planet. Volcanic eruptions constitute one of the more dangerous natural hazards in the world, as illustrated by such eruptions as Vesuvius in AD 79, which ruined Pompeii and Herculaneum; the explosion of Krakatoa in Indonesia in 1883; and the directed blast of Mt. St. Helens volcano (USA) in 1980. Millions of people in the world live in the vicinity of active volcanoes. Cities such as Naples in Italy,UNESCO Kagoshima in Japan, Hilo on– Hawaii, EOLSS and many others are located near active volcanoes as are densely populated agricultural districts in Indonesia, the Philippines, Japan, Mexico, and other countries. Assessment of the hazard through the prediction of eruptions and an understanding of their power and character allows vitally important protectiveSAMPLE measures to be undertaken. CHAPTERS Traditionally a volcano has been termed “active” if it has historically recorded eruption(s). But different volcanic regions have different duration of historical record; in Italy for example, the earliest known documentated eruption of Etna volcano goes back to 1500 BC while in Kamchatka historical records of eruption began from the eighteenth century. Moreover, many volcanoes are remote from human habitation and have only poorly documented historic eruptions. Volcanic eruption repose periods are often many hundreds of years, and major eruptions may be separated by thousands of years. Szakacs suggested the following empirical redefinition of an active volcano: “A ©Encyclopedia of Life Support Systems (EOLSS) NATURAL AND HUMAN INDUCED HAZARDS – Vol. I - Geography of Volcanic Zones and Distribution of Active Volcanoes - V. Yu. Kirianov volcano is termed active if it has erupted at least once during the last 10 000 years or, alternatively, 5000 or 2000 years as demonstrated by any scientific method.” Many catalogues and listings of active volcanoes and their eruptions have been made. Among the first such list was that published by the geographer Varenius (Bernhard Varen) in 1650. In more modern times, the German volcanologist Sapper produced a monumental catalog of the world’s volcanoes in 1917. By 1960, the Volcanological Society of Japan began recording the new eruptions of the world by publishing a yearly Bulletin of Volcanic Eruptions. More immediate notification of eruptions began in 1968 when the Smithsonian Institution started the Center for Short-Lived Phenomena. Renamed the Scientific Event Alert Network (SEAN) by the Smithsonian in 1975, this group now issues a monthly Bulletin describing current eruptive activity. Volcanism is truly one of the grand forces of nature that has greatly affected the environment of the world in which we live. One of the keys to understanding volcanic processes is to study the distribution of volcanoes and the geologic setting in which they occur. A map of the world’s active volcanoes shows them to be distributed unequally on the earth’s surface, concentrated in some areas and completely lacking in others. UNESCO – EOLSS Figure 1. Distribution of volcanoes of the world SAMPLEFrom T. Simkin and L.CHAPTERS Siebert (1994) This distribution characteristic has been correlated with structures of almost global proportions as well as those with purely local geologic conditions. Another highly visible feature of the global distribution of volcanoes is their concentration around the margin of the Pacific Ocean forming the so-called “Ring of Fire” ©Encyclopedia of Life Support Systems (EOLSS) NATURAL AND HUMAN INDUCED HAZARDS – Vol. I - Geography of Volcanic Zones and Distribution of Active Volcanoes - V. Yu. Kirianov Figure 2. Volcanic arcs and oceanic threnches partly encircling the Pacific Basin form the so-called Ring of Fire, a zone of volcanic eruptions (archive USGS) About 62% of all active volcanoes in the world are located around the margins of the Pacific Ocean, although their distribution along this rim is irregular. The East Pacific Island Arc, for example, includes 45% of the world’s active volcanoes while the Central and South America segments contain only 17% of the volcanoes. About 14% of the volcanoes are located in the Indonesian Islands arc while, of the remaining 24%, 3% are located in the mid-Pacific Ocean, 1% in mid-Indian Ocean islands, 13% on mid-Atlantic Ocean islands, and the last 7% scattered through the Mediterranean Sea and Central Asia (Turkey, Iraq, etc.) and the inner part of continents, for example, the African Rift. It is possible to divide the volcanoes of the world into seven regions as follows: (1) volcanoes of the Pacific Ocean island arcs and Alaska continental rim,(2) volcanoes of the East Pacific continental rim, (3) volcanoes of alpine-Indonesian mountain belt, (4) volcanoes of East African–Arabian belt, (5) volcanoes of the rifts and mountains of Eurasia, (6) volcanoes of the West Indies island arc, and (7) volcanoes of the ocean floor. UNESCO – EOLSS 2. Volcanoes of the Pacific Ocean Island Arcs and Alaska Continental Rim Island arcs are oneSAMPLE of the more intriguing features CHAPTERS on Earth’s surface. Many theories had been offered in the past to explain them, but the concept of seafloor spreading as developed in the 1960s and 1970s provides the best explanation for their origin and associated volcanism. The Pacific Ocean island arcs consist of chains of volcanic islands hundreds to thousands of kilometers long located above deep-seated megacrust faults that reach deep into Earth’s mantle and are marked by the deep trenches of the world’s oceans. Many of these island chains intersect to form the famous Pacific ring of fire, which extends for thousands of kilometers across Earth’s surface. Thousands of volcanoes along this ring have been active in the Quaternary and at least 380 of them are considered to be presently active. In the north Pacific, the Aleutian Island arc ©Encyclopedia of Life Support Systems (EOLSS) NATURAL AND HUMAN INDUCED HAZARDS – Vol. I - Geography of Volcanic Zones and Distribution of Active Volcanoes - V. Yu. Kirianov continues onto the continental margin of Alaska forming the composite Aleutian volcanic arc. Active volcanoes along the west margin of the Pacific Ocean are concentrated along a variety of island arcs with these definitions. Frontal arcs are as long as 3000–4000 km and result from subduction of oceanic crust on the oceanic side of the arc; they are accompanied by deep ocean trenches. Various arc systems intersect each other at angles up to 90o.